draft-ietf-idr-custom-decision-01.txt   draft-ietf-idr-custom-decision-02.txt 
Inter-Domain Routing A. Retana Inter-Domain Routing A. Retana
Internet-Draft Hewlett-Packard Co. Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track R. White Intended status: Standards Track R. White
Expires: November 19, 2012 Verisign Expires: May 20, 2013 Verisign
May 18, 2012 November 16, 2012
BGP Custom Decision Process BGP Custom Decision Process
draft-ietf-idr-custom-decision-01 draft-ietf-idr-custom-decision-02
Abstract Abstract
The BGP specification defines a Decision Process for installation of The BGP specification defines a Decision Process for installation of
routes into the Loc-RIB. This process takes into account an routes into the Loc-RIB. This process takes into account an
extensive series of path attributes, which can be manipulated to extensive series of path attributes, which can be manipulated to
indicate preference for specific paths. It is cumbersome (if at all indicate preference for specific paths. It is cumbersome (if at all
possible) for the end user to define policies that will select, after possible) for the end user to define policies that will select, after
partial comparison, a path based on subjective local (domain and/or partial comparison, a path based on subjective local (domain and/or
node) criteria. node) criteria.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 19, 2012. This Internet-Draft will expire on May 20, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . . 3
3. The BGP Cost Community . . . . . . . . . . . . . . . . . . . . 3 3. The BGP Cost Community . . . . . . . . . . . . . . . . . . . . 4
4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 5 5. Deployment Considerations . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7 9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . . 7 9.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Cost Community Point of Insertion Registry . . . . . . 7 Appendix A. Cost Community Point of Insertion Registry . . . . . . 7
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . . 8 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 B.1. Changes between the -00 and -01 versions. . . . . . . . . . 8
B.2. Changes between the -01 and -02 versions. . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
There are a number of metrics available within the BGP decision There are a number of metrics available within the BGP decision
process [RFC4271] which can be used to determine the exit point for process [RFC4271] which can be used to determine the exit point for
traffic, but there is no metric, or combination of metrics, which can traffic, but there is no metric, or combination of metrics, which can
be used to break a tie among generally equal paths. be used to break a tie among generally equal paths.
o LOCAL_PREF: The LOCAL_PREF is an absolute tie breaker near the o LOCAL_PREF: The LOCAL_PREF is an absolute tie breaker near the
beginning of the decision process. There is no way to configure beginning of the decision process. There is no way to configure
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130 EXTERNAL_INTERNAL - Indicates that the Cost Community MUST 130 EXTERNAL_INTERNAL - Indicates that the Cost Community MUST
be considered after the paths advertised by BGP speakers in be considered after the paths advertised by BGP speakers in
a neighboring autonomous system (if any) have been selected. a neighboring autonomous system (if any) have been selected.
131 BGP_ID - Indicates that the Cost Community MUST be 131 BGP_ID - Indicates that the Cost Community MUST be
considered after the BGP Identifier (or ORIGINATOR_ID considered after the BGP Identifier (or ORIGINATOR_ID
[RFC4456]) has been compared. [RFC4456]) has been compared.
The Community-ID sub-field contains an identifier to distinguish The Community-ID sub-field contains an identifier to distinguish
between multiple instances of the Cost Community. between multiple instances of the Cost Community. The high-order
bit is reserved to indicate that the Cost Community MUST replace
the path attribute specified by the Point of Insertion during the
best path selection process.
The Cost sub-field contains a value assigned by the network The Cost sub-field contains a value assigned by the network
administrator and that is significant to the local autonomous administrator and that is significant to the local autonomous
system. The lower cost MUST be preferred. The default value is system. The lower cost MUST be preferred. The default value is
0x7FFFFFFF (half the maximum value). 0x7FFFFFFF (half the maximum value).
4. Operation 4. Operation
The network administrator may use the Cost Community to assign a The network administrator may use the Cost Community to assign a
value to a path originated or learned from a peer in any part of the value to a path originated or learned from a peer in any part of the
local domain. The Point of Insertion is also specified using the local domain. The Point of Insertion MUST also be specified using
values defined in Appendix A. the values defined in Appendix A.
If a BGP speaker receives a path that contains the Cost Community, it If a BGP speaker receives a path that contains the Cost Community, it
SHOULD consider its value at the Point of Insertion specified, when SHOULD consider its value at the Point of Insertion specified, when
calculating the best path [RFC4271]. calculating the best path [RFC4271].
If the Point of Insertion is not valid for the local best path If the Point of Insertion is not valid for the local best path
selection implementation, then the Cost Community SHOULD be silently selection implementation, then the Cost Community SHOULD be silently
ignored. Paths that do not contain the Cost Community (for a valid, ignored. Paths that do not contain the Cost Community (for a valid,
particular Point of Insertion) MUST be considered to have the default particular Point of Insertion) MUST be considered to have the default
value. value.
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In this case, the Cost Community with the lowest Community-ID is In this case, the Cost Community with the lowest Community-ID is
considered first. In other words, all the Cost Communities for a considered first. In other words, all the Cost Communities for a
specific Point of Insertion MUST be considered, starting with the one specific Point of Insertion MUST be considered, starting with the one
with the lowest Community-ID. with the lowest Community-ID.
If a range of routes is to be aggregated and the resultant aggregate If a range of routes is to be aggregated and the resultant aggregate
path attributes do not carry the ATOMIC_AGGREGATE attribute, then the path attributes do not carry the ATOMIC_AGGREGATE attribute, then the
resulting aggregate SHOULD have an Extended Communities path resulting aggregate SHOULD have an Extended Communities path
attribute which contains the set union of all the Cost Communities attribute which contains the set union of all the Cost Communities
from all of the aggregated routes. If multiple Cost Communities for from all of the aggregated routes. If multiple Cost Communities for
the same Point of Insertion (and with the same Community-ID), then the same Point of Insertion (and with the same Community-ID) exist,
only the ones with the highest Cost SHOULD be included. then only the ones with the highest Cost SHOULD be included.
If the non-transitive version of a Cost Community is received across If the non-transitive version of a Cost Community is received across
an Autonomous System boundary, then the receiver MUST strip it off an Autonomous System boundary, then the receiver MUST strip it off
the BGP update, and ignore it when running the selection process. the BGP update, and ignore it when running the selection process.
5. Deployment Considerations 5. Deployment Considerations
The mechanisms described in this document may be used to modify the The mechanisms described in this document may be used to modify the
BGP path selection process arbitrarily. It is important that a BGP path selection process arbitrarily. It is important that a
consistent path selection process be maintained across the local consistent path selection process be maintained across the local
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| 128 | ABSOLUTE_VALUE | draft-ietf-idr-custom-decision | | 128 | ABSOLUTE_VALUE | draft-ietf-idr-custom-decision |
| 129 | IGP_COST | draft-ietf-idr-custom-decision | | 129 | IGP_COST | draft-ietf-idr-custom-decision |
| 130 | EXTERNAL_INTERNAL | draft-ietf-idr-custom-decision | | 130 | EXTERNAL_INTERNAL | draft-ietf-idr-custom-decision |
| 131 | BGP_ID | draft-ietf-idr-custom-decision | | 131 | BGP_ID | draft-ietf-idr-custom-decision |
+--------+-------------------+--------------------------------+ +--------+-------------------+--------------------------------+
Point of Insertion Codes Point of Insertion Codes
Appendix B. Change Log Appendix B. Change Log
The following are the changes with respect to the -00 version. B.1. Changes between the -00 and -01 versions.
o Updated authors' contact information. o Updated authors' contact information.
o Editorial changes in the "Operations" and "Acknowledgement" o Editorial changes in the "Operations" and "Acknowledgement"
sections. sections.
B.2. Changes between the -01 and -02 versions.
o Updated authors' contact information.
o Added text to replace a step in the selection process.
o Minor edits.
Authors' Addresses Authors' Addresses
Alvaro Retana Alvaro Retana
Hewlett-Packard Co. Cisco Systems, Inc.
2610 Wycliff Road 7025 Kit Creek Rd.
Raleigh, NC 27607 Research Triangle Park, NC 27709
USA USA
Email: alvaro.retana@hp.com Email: aretana@cisco.com
Russ White Russ White
Verisign Verisign
12061 Bluemont Way 12061 Bluemont Way
Reston, VA 20190 Reston, VA 20190
USA USA
Email: riwhite@verisign.com Email: riwhite@verisign.com
 End of changes. 14 change blocks. 
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